If you're running a ~ arch, DO NOT update to glibc-2.13 if you have prelink installed!!! It will completely hose your box!!! I just spent several hours trying to recover from this bug https://bugs.gentoo.org/show_bug.cgi?id=353814

If you want the new glibc, you must first uninstall prelink or if you want to keep prelink, you need to mask the new glibc until one or the other is fixed.

When I updated yesterday morning glibc was in the queue. It installed without issues. I then 'emerge -eavND @system' to rebuild against it. Halfway through the emerge, portage crashed, bash segfaulted and my KDE DE ceased functioning. I tried to ssh into my box, but it was impossible because all of my network connections ceased functioning. The only way to get out of X was a hard reboot, but then all three of my kernels panicked just after leaving the grub splash.

I was finally able to regain control of my machine by booting into a rescue disc and following the instructions posted in comment #3 in the bug report I linked to. I had to chroot into my box to uninstall prelink, before I was able to regain control and reboot back into my system.

Yes it sucks, but prelink is run by a cron job. Until prelink is run, everything appears to work. No amount of testing would catch it unless the cron job happened to trigger._________________by design, by neglect
for a fact or just for effect